Pressure relief valves are used in a variety of commercial, industrial and domestic applications to maintain a pressure within a container below a predetermined maximum pressure. Specifically, if the pressure within the container exceeds a start-to-discharge pressure or predetermined maximum pressure, the pressure relief valve will vent a fluid or vapor to the atmosphere until the pressure within the container decreases below the predetermined maximum pressure. The amount and rate at which the fluid or vapor is vented to the atmosphere is associated with the magnitude of the pressure within the container.
Different pressure relief valves have different sizes, start-to-discharge pressures and flow capacities. A pressure relief valve may be selected for use with a container based on a design specification of the container such as a maximum pressure to which the container can be safely exposed without rupturing.
Known pressure relief valves often include a single spring that exerts a force on a shaft to urge a valve seat towards a seating surface. Containers that have a relatively high maximum pressure require a pressure relief valve that has a spring with a relatively large spring rate to maintain the position of the valve seat relative to the seating surface. Typically, in known pressure relief valve applications, springs with relatively large spring rates are considerably longer (e.g., have a larger length) than springs with relatively small spring rates. As a result, pressure relief valves that require a spring with a relatively large spring rate significantly increase the overall size and length of the pressure relief valve. In practice, if a plurality of pressure relief valves are used with a manifold assembly, each of the plurality of pressure relief valves is at least partially positioned within one of a plurality of tubes coupled to the manifold assembly. Typically, each tube is substantially the same length as the pressure relief valve and is made of a metal material and, thus, the length and weight of the pressure relief valve drastically impacts the overall weight and size (e.g., height) of the manifold assembly.
Additionally, springs with relatively large spring rates are typically made of a material that has a significantly higher yield stress as compared to springs with relatively small spring rates. Depending on the environment in which the pressure relief valve is used, springs made with material that has a relatively high yield stress may be susceptible to hydrogen embrittlement. Hydrogen embrittlement decreases the life of the spring and may enable the pressure relief valve to malfunction and vent fluid or vapor to the atmosphere when the pressure within the chamber is below the start-to-discharge pressure.